How do I access a property of the Event element in Javascript?

I think it's a silly question, but from my beginner knowledge I'm beating a little. I'm building an application in ionic3, this uses typescript, however the plugin I'm working on uses pure javascript. In my console I can display all the properties of "event", but how do I display a specific property of those? The property I need is marked in yellow "rewardAmount".

videosAdColony(){letcarregar=this.loading.create({content:"Carregando..."});
    carregar.present();
    let rewardConfig: AdMobFreeRewardVideoConfig = {
        isTesting: true,
        autoShow: true,
        id: 'ca-app-pub-8000726989219599/8229278077' //id videos AdColony
    };
    this.admob.rewardVideo.config(rewardConfig);
    this.admob.rewardVideo.prepare().then(() => {
        console.log('video adcolony executado com sucesso');
        carregar.dismissAll();
        document.addEventListener('admob.rewardvideo.events.REWARD', function (event) {

            console.log(event);
        })
    })
}